1. Field of the Invention
This invention relates to a golf club head.
2. Description of the Related Art
Conventionally, as methods for fixing a golf club head main body and a face body which is fitted to a concave portion of a face side of the head main body, techniques of 1 through 5 do described below are known.
1 Japanese Patent Provisional Publication No. 6-165843 discloses a golf club head in which a face body is fixed to a head main body through metal members for connection.
2 Japanese Patent Provisional Publication No. 6-182006 discloses a golf club head in which a concave portion is formed on a face body, a convex portion which fits to the concave portion is formed on a head main body with plastic deformation, and the face body is fixed to the head main body.
3 Japanese Patent Provisional Publication No. 5-337222 discloses a golf club head in which a peripheral face of a concave portion of a head main body to which a face body is attached is formed with a reverse-tapered configuration as to be wider at a back side, and the face body is press-fitted to the concave portion with plastic deformation and fixed to the head main body.
4 Japanese Patent Provisional Publication No. 7-255884 discloses a golf club head in which pins are applied to a concave portion of a head main body to which a face body is fitted, pin holes where the pins go through are disposed on the face body, and the face body is fixed to the head main body with caulking the pins.
5 Japanese Patent Provisional Publication No. 8-252344 discloses a golf club head in which a caulking member is applied to an aperture between an inner face of a concave portion of a head main body and a circumference of a face body, and the face body is fixed to the head main body with plastic deformation of the caulking member.
In recent years, golf clubs in which dissimilar (different) metals are combined have been attracting public attention. As effects of using dissimilar metals, increase of degree of freedom in weight distribution, efficient use of small amount of expensive materials (such as titanium alloy etc.), proper selection of materials corresponding to requirement characteristics of each part of a head (strength, rigidity, wear rate etc.), and external beauty, are thinkable. To realize a combination head made of dissimilar metals as described above, various methods for fixing a face body to a head main body have been proposed as described above.
Problems described below, however, still remain unsolved.
That is to say, in case that titanium alloy, which is attracting attention as a head material, is used for a head main body or a face body, and a material which is difficult to be worked plastically (such as pure titanium, tungsten, ceramic, amorphous metal, etc.) is used for the other, it is difficult to fix the face body to the head main body by fixing methods with plastic deformation shown in above described 2 and 3. Because titanium and titanium alloy have high deformation resistance in plastic deformation, bad dimension accuracy for their high spring back, and are considerably difficult to be worked plastically in comparison with conventional materials. And if titanium and titanium alloy are forced to be fixed with plastic deformation (caulking), gaps may be generated by relieves of caulked parts.
In fixing methods of 1 and 4, a face body can be fixed to a head main body when they are made of materials which is difficult to be plastically deformed, since the fixation is conducted with metal members for connection or pins. In these methods, however, number of parts increases for necessity of the metal members for connection, the pins, and the pin holes to which the pins are inserted. This increases parts preparation time and number of assemble processes, production efficiency becomes worse, and production cost becomes higher thereby.
In fixing methods of 5 in which the face body and the head main body are connected by plastic deformation of the caulking member applied to the aperture between the inner face of the concave portion of the head main body and the circumference of the face body (a face insert), although a head main body and a face body made of materials which are difficult to be plastically deformed can be fixed, following problems still remain.
That is to say, position of the face body moves, and an aperture between the inner peripheral surface of the head main body and the peripheral face of the face body becomes ununiform in peripheral direction with the plastic deformation of the caulking member in press working, because positioning of the face body to the head main body depends on the plastic deformation of the caulking member. And, in case that the caulking member is partially worked with plastic deformation with sequential move of press position, the face body is greatly dislocated and the aperture becomes extremely ununiform.
For this reason, it is necessary to deform the caulking member entirely at the same time, and a large press apparatus is required. However, it is difficult to deform the entire caulking member uniformly at the same time, even with a large press apparatus, and the dislocation of the face body conspicuously appears for ununiformity of pressure, etc.
And, another problem is that impact force when the club head hits a golf ball generates elastic deformation in the face body, and the club head is damaged by deformation and rubbing of the caulking member, of which material is easily deformed plastically, filling the aperture between the inner face of the concave portion of the head main body and the circumference of the face body. And, there is a further problem that gaps are generated between the caulking member and the face body (an insert body).
It is therefore an object of the present invention to provide a golf club head in which a head main body and a face body made of low plasticity materials can be fixed with high working efficiency by a small manufacturing apparatus. And, it is another object of the present invention to provide a golf club head which does not generate dislocation of the face body, even if the caulking member is worked with partial plastic deformation sequentially, and having beautiful finish, high fixation ability of the face body, and high durability.